基于2006—2015年上市公司的面板数据,在Aghion et al.[1]的经验模型基础上引入企业所有制变量,并采用SA指数衡量企业研发投入的外部融资约束程度,检验了融资约束条件下企业所有制对其研发投入周期性的平滑机制。实证结果表明,存在融资...基于2006—2015年上市公司的面板数据,在Aghion et al.[1]的经验模型基础上引入企业所有制变量,并采用SA指数衡量企业研发投入的外部融资约束程度,检验了融资约束条件下企业所有制对其研发投入周期性的平滑机制。实证结果表明,存在融资约束时研发投入的逆周期性减弱,融资约束程度越严重,其顺周期性越强;进一步得出中国上市公司研发投入的以下特征事实:(1)在经济高涨时期,研发投入有更强的融资约束效应,但由于有机会利用股权融资等其他非债务融资渠道,此时研发投入的顺周期性也更强;(2)国有产权属性对研发投入的融资约束效应和顺周期性都有平滑作用,且只对顺周期性有显著的不对称平滑作用,即对经济高涨时期顺周期性的平滑作用更显著。同时,这种不对称的平滑作用对宏观经济波动的顺周期反应更为明显。展开更多
A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can eas...A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can easily be exfoliated from the surface of the matrix due to weak holding-force with matrix, which made the surface non-smooth. Three Ф36/24 mm laboratorial bits were manufactured to conduct a laboratory drilling test on zirconiacorundum refractory brick. The laboratory drilling test indicates that the abrasive resistance of the bit work layer is proportional to the Si C concentation. The higher the concentration, the weaker the abrasive resistance of matrix. The new impregnated diamond bit was applied to a mining area drilling construction in Jiangxi province, China. Field drilling application indicates that the ROP(rate of penetration) of the new bit is approximately two to three times that of the common bits. Compared with the common bits, the surface of the new bit has typical abrasive wear characteristics,and the metabolic rate of the diamond can be well matched to the wear rate of the matrix.展开更多
文摘基于2006—2015年上市公司的面板数据,在Aghion et al.[1]的经验模型基础上引入企业所有制变量,并采用SA指数衡量企业研发投入的外部融资约束程度,检验了融资约束条件下企业所有制对其研发投入周期性的平滑机制。实证结果表明,存在融资约束时研发投入的逆周期性减弱,融资约束程度越严重,其顺周期性越强;进一步得出中国上市公司研发投入的以下特征事实:(1)在经济高涨时期,研发投入有更强的融资约束效应,但由于有机会利用股权融资等其他非债务融资渠道,此时研发投入的顺周期性也更强;(2)国有产权属性对研发投入的融资约束效应和顺周期性都有平滑作用,且只对顺周期性有显著的不对称平滑作用,即对经济高涨时期顺周期性的平滑作用更显著。同时,这种不对称的平滑作用对宏观经济波动的顺周期反应更为明显。
基金Project(51074180)supported by the National Natural Science Foundation of China
文摘A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can easily be exfoliated from the surface of the matrix due to weak holding-force with matrix, which made the surface non-smooth. Three Ф36/24 mm laboratorial bits were manufactured to conduct a laboratory drilling test on zirconiacorundum refractory brick. The laboratory drilling test indicates that the abrasive resistance of the bit work layer is proportional to the Si C concentation. The higher the concentration, the weaker the abrasive resistance of matrix. The new impregnated diamond bit was applied to a mining area drilling construction in Jiangxi province, China. Field drilling application indicates that the ROP(rate of penetration) of the new bit is approximately two to three times that of the common bits. Compared with the common bits, the surface of the new bit has typical abrasive wear characteristics,and the metabolic rate of the diamond can be well matched to the wear rate of the matrix.
